In vitro fertilization (IVF) provides a unique opportunity to isolate and observe certain human reproductive processes, and thus potentially to differentiate among possible mechanisms of reproductive toxicity. In this clinical protocol, the woman undergoes pharmacologic hyperstimulation of her ovaries, and multiple ova are surgically extracted and fertilized in a dish, usually with her husband's sperm. Thus, the quality of each ovum is assessed, rates of fertilization and cleavage can be studied, early development of the embryos can be observed, and finally implantation into the uterus can be assessed, after the transfer of a known number of embryos. In collaboration with staff at UNC School of Medicine, we undertook a study to relate exposures to clinical outcomes in IVF. Although the patients are themselves infertile, this clinical protocol allows us potentially to demonstrate effects of certain exposures, such as caffeine, on specific reproductive processes. We have now completed the analysis of number of ova harvested, and fertilization and cleavage of the ova and are revising a paper for publication.